Mycotoxins in South African foods: a case study on aflatoxin M1 in milk.

The contamination of cow's milk at the farm level with aflatoxin M1 was investigated in South Africa. Samples of feeds, forage, maize and milk were taken at nine dairy farms, and at the same time samples of the processed milk (retail milk) were collected from the respective dairies to which the farms delivered their milk. The feeds were analysed for aflatoxin B1 and the milk samples for aflatoxin M1 using high performance liquid chromatography (HPLC) and fluorescence detection. All milk samples from the dairy farms were positive for aflatoxin M1, ranging from 0.02 µg/l to 1.5 µg/l. Retail milk was also frequently contaminated with AFM1, at levels of 0.01-3.1 µg/l. High AFB1 levels in feed materials on the farms supplying the raw milk indicate that various sources account for this contamination frequency in milk.

Natural multi-occurrence of mycotoxins in rice from Niger State, Nigeria.

Twenty-one rice samples from field (ten), store (six) and market (five) from the traditional rice-growing areas of Niger State, Nigeria were analysed for aflatoxins (AFs), ochratoxin A (OTA), zearalenone (ZEA), deoxynivalenol (DON), fumonisin B(1) (FB(1)) and B(2) (FB(2)), and patulin (PAT) by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) respectively. T-2 toxin was determined using TLC only. AFs were detected in all samples, at total AF concentrations of 28-372 µg/kg. OTA was found in 66.7% of the samples, also at high concentrations (134-341 µg/kg) that have to be considered as critical levels in aspects of nephrotoxicity. ZEA (53.4%), DON (23.8), FB(1) (14.3%) and FB(2) (4.8%) were also found in rice, although at relatively low levels. T-2 toxin was qualitatively detected by TLC in only one sample. Co-contamination with AFs, OTA, and ZEA was very common, and up to five mycotoxins were detected in a single sample. The high AF and OTA levels as found in rice in this study are regarded as unsafe, and multi-occurrences of mycotoxins in the rice samples with possible additive or synergistic toxic effects in consumers raise concern with respect to public health.

The cytotoxic effect of fumonisin B1 and ochratoxin A on human and pig lymphocytes using the Methyl Thiazol Tetrazolium (MTT) assay.

Lymphocytes cell obtained from healthy human donors and pigs were exposed to fumonisin B1 (FB1) and ochratoxin A (OTA), which have been found to be immunosuppressive, carcinogenic and mutagenic, to ascertain their single and combined cytotoxic effects with time and to assess the suitability of animal lymphocytes as test agents in comparison to human cells. The main objectives of this work were to assess the use of animal lymphocytes, particularly pig lymphocytes, for their use in the Methyl Thiazol Tetrazolium (MTT) cytotoxicity test, making them more accessible to animal research-based institutes in comparison to human lymphocytes previously used, and to study the cytotoxic and synergism or antagonistic effects of FB1 and OTA. The MTT assay, which measures cell viability and proliferation based on reduction of MTT to a blue dye, also used the addition of phytohaemagglutinin (PHA) to stimulate the blood cells. The results showed a progressive decrease in lymphocytes viability with time of exposure to the toxins. It was also noted that FB1, as compared to OTA, had a lower cytotoxicity on both human and pig lymphocytes cells. In addition, when the two mycotoxins were combined, a synergistic decrease of cell viability in both human and pig lymphocytes was observed, with pig lymphocytes showing a greater sensitivity. This study has shown that the MTT assay can be used for the determination of cytotoxicity of mycotoxins using animal, and in particular pig, lymphocytes, which eliminates the use of human donors and other cell cultures.